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Evaluating the Temporal Stability of Gene Expression Endpoints with Repeated Sampling Up and Down Stream of a Wastewater Treatment Plant
Citation:
Biales, A., J. Stelman, W. Huang, S. Glassmeyer, D. Kolpin, E. Furlong, M. Mills, Mary Jean See, D. Bencic, R. Flick, AND Tom Purucker. Evaluating the Temporal Stability of Gene Expression Endpoints with Repeated Sampling Up and Down Stream of a Wastewater Treatment Plant. SETAC North America 42nd Annual meeting, Portland, OR, November 14 - 18, 2021. https://doi.org/10.23645/epacomptox.17114027
Impact/Purpose:
Presentation to the SETAC North America 42nd Annual meeting November 2021. Demonstrates the robustness of gene expression to characterize a complex source of chemical pollutants
Description:
Transcriptomic endpoints are increasingly being used in environmental toxicology and monitoring. Laboratory-based studies generally are highly controlled and aim to evaluate a select number of chemicals or conditions, limiting the effects of confounding factors. This makes it possible to directly link the experimental condition with the response and greatly simplifies interpretation of transcriptomic responses. In contrast, interpretation of field-based studies is complicated by the temporal dynamics of source inputs, water quality, and considerable unknowns in chemical exposures. While previous research used transcriptomic endpoints to evaluate potential deleterious effects or as biomarkers of contaminant exposures in aquatic environments, few (if any) such research sought to characterize the stability of global gene expression in field applications. Our study aimed to characterize the stability of gene expression in three commonly used applications: (1) source characterization, (2) exposure biomarkers, and (3) effect characterization. Gene expression was compared between five treatments of matched groups of exposed larval fathead minnow (FHM; Pimephales promelas) exposed to water upstream from and within the effluent of a wastewater treatment plant. Four treatments consisted of grab samples taken in the morning and afternoon over two consecutive days and brought back for static exposures under controlled ambient conditions. The fifth treatment consisted of in situ exposed organisms deployed at the same site and time as the grab samples. RNA sequencing analysis was conducted on whole FHM larvae. Statistical enrichment of overlap among time points and exposure treatments were identified by examining the multi-set intersections of differentially expressed transcripts versus a combinatorial-based null model. Classifiers were developed for each time-matched upstream and downstream pair using several common classification algorithms which were tested on their ability to classify other time-matched pairs and the in situ exposure. To evaluate consistency in the biological response, functional enrichment was also conducted for each of the time-matched pairs. This analysis demonstrates the robustness and stability of gene expression biomarkers in common application and exposure scenarios and may provide important insight into the limits of interpretation of transcriptomic endpoints.
URLs/Downloads:
DOI: Evaluating the Temporal Stability of Gene Expression Endpoints with Repeated Sampling Up and Down Stream of a Wastewater Treatment Plant
SETAC_2021.PDF (PDF, NA pp, 2020.708 KB, about PDF)